Last modified: December 2021

AHELP for CIAO 4.14 Sherpa


Context: models


The XSPEC grbjet model: Two-phase Comptonization model of soft thermal seed photons for GRB prompt emission



The xsgrbjet model is an additive model component.


The model is described at [1] .


>>> create_model_component("xsgrbjet", "mdl")
>>> print(mdl)

Create a component of the xsgrbjet model and display its default parameters. The output is:

   Param        Type          Value          Min          Max      Units
   -----        ----          -----          ---          ---      -----
   mdl.thobs    frozen            5            0           30           
   mdl.thjet    frozen           10            2           20           
   mdl.gamma    thawed          200            1          500           
   mdl.r12      frozen            1          0.1          100           
   mdl.p1       thawed            0           -2            1           
   mdl.p2       thawed          1.5          1.1           10           
   mdl.E0       thawed            1          0.1         1000        keV    frozen          0.2         0.01          1.5           
   mdl.index_pl frozen          0.8            0          1.5           
   mdl.ecut     frozen           20          0.1         1000        keV
   mdl.ktbb     frozen            1          0.1         1000        keV
   mdl.model    frozen            1 -3.40282e+38  3.40282e+38           
   mdl.redshift frozen            2        0.001           10           
   mdl.norm     thawed            1            0        1e+24           


The attributes for this object are:

Attribute Definition
thobs The observing viewing angle in degrees.
thjet The jet half-opening angle in degrees.
gamma The jet gamma Lorentz factor.
r12 The jet radius in 10^12 cm.
p1 The low-energy index of the coming frame broken powerlaw spectrum.
p2 The high-energy index of the coming frame broken powerlaw spectrum.
E0 The break energy in keV.
delta The smoothness of the transition between the two powerlaws.
index_pl The energy index of the comoving-frame cutoff powerlaw spectrum.
ecut The cut-off energy in keV.
ktbb The comoving frame blackbody temperature in keV.
model The comoving frame emissivity law: 1 is broken powerlaw, 2 is cutoff powerlaw, and 3 is blackbody.
redshift The source redshift.
norm The normalization of the model: see [1] for an explanation of the units.


Changes in CIAO

New in CIAO 4.14

The xsgrbjet model (added in XSPEC 12.12.0) is new in CIAO 4.14.

XSPEC version

CIAO 4.14 comes with support for version 12.12.0 of the XSPEC models. This can be checked with the following:

% python -c 'from sherpa.astro import xspec;


See the bugs pages on the Sherpa website for an up-to-date listing of known bugs.

See Also

xsgrbcomp, xsgrbm